1. Field of the Invention
The present invention relates to a method for repairing a honeycomb core sandwich panel having a configuration in which a honeycomb structured core is held between outer skins, and an apparatus for repairing the same.
2. Description of the Related Art
Since a honeycomb core sandwich panel in which thin outer skins are attached to both surfaces of a honeycomb structured core is lightweight and highly rigid, the honeycomb core sandwich panel is usually used for the structure of an aircraft. A composite material of FRP (fiber reinforced plastics) or the like is often used as the outer skin of the honeycomb core sandwich panel.
However, the thin outer skin is easily damaged by a lightning strike, or a flying object such as hail.
Japanese Patent Laid-Open No. 3-264356 discloses a method for repairing a honeycomb core sandwich panel in which a honeycomb structured core is held between FRP plates. When the core and the FRP plate are separated from each other, moisture existing in a separated portion between the core and the FRP plate is removed by decompressing the separated portion by vacuum drawing. The separated portion is then filled with resin for repair, so that the core and the FRP plate are bonded together without being disturbed by moisture.
When the honeycomb core sandwich panel is repaired, a repair material is disposed on a repair target portion that has been formed by damage. Thermosetting resin is used for the repair material. The repair material is heated and cured.
At this time, to reliably cure the repair material, the panel is maintained at a high temperature. Accordingly, moisture accumulated in cells or on partition walls of the core of the panel changes into water vapor to generate a high pressure within the cells. The panel may be destroyed by the pressure.
Even when moisture existing in the separated portion between the core and the FRP plate is removed as described in Japanese Patent Laid-Open No. 3-264356, moisture remains within the core. Thus, there is still a possibility that the panel is destroyed at the time of heating for repair.
Therefore, to reliably prevent the panel from being destroyed, a drying step for the purpose of sufficiently drying the core is performed before heating. However, it takes a very long time to repair the panel due to the drying step.
An object of the present invention is to reduce a time required for repairing the honeycomb core sandwich panel while avoiding the destruction of the honeycomb core sandwich panel at the time of repair.